Three British men were jailed last year for drug offences in Dubai and subsequently pardoned after also claiming that they had been tortured by police. Photograph: John Philip Harper/Getty

Details of torture allegedly inflicted on two Britons by police in the United Arab Emirates have emerged in Foreign Office documents which suggest that one was subjected to a "kicking" from officers who had earlier held a gun to his head.

Ahmad Zeidan, 20, a student from Berkshire, was arrested on drugs charges – which he denies – and alleges that he was beaten, hooded, stripped naked and threatened with rape by police officers.

Hasnain Ali, 32, from London, was also arrested on contested drugs allegations. The former bodyguard to Emirati royals claims that he was beaten, kicked and threatened with Tasers.

Both say they were made to sign documents in Arabic that neither could read. Ali learned later that he had confessed to drugs offences, which potentially carry the death penalty.

Documents obtained following a visit by Foreign Office officials to Ali in Dubai Central Prison shed light on some of the allegations, including one that police officers "hit his head from the left side and pointed a gun to his head".

Ali, who has been employed in protecting Shaikha Fatima bint Mubarak, mother of the crown prince of Abu Dhabi – the family's assets include Manchester City football club – also alleged that he was "repeatedly kicked by the officers". He said that he "found bruises on his back that were a result of his kicking".

Later the document describes how Ali took off his T-shirt to show officials "four even scars, two on the right side and two on the left, parallel to each other".

The Foreign Office diplomats also observe that Ali displayed an apparent fear of the Dubai police officers, noting that while they were in the cell he did not make complaints against them but "looked at the officers when saying this, and had tears in his eyes".

The UAE is known for its hardline approach to narcotics and alcohol. A 33-year-old British man appeared in court in Dubai last week accused of getting drunk and running naked through a building on the Palm Jumeirah.

Clare Algar of legal charity Reprieve, which is representing the two men, said: "Police torture is out of control in the UAE. Dubai and its fellow emirates have persistently refused to carry out independent investigations into these abuses, and seem content to let their police continue beating and threatening people into signing bogus 'confessions'."

Three British men were jailed last year for drug offences in Dubai. They were subsequently pardoned after also claiming that they had been tortured by police following their arrest while on holiday in the Gulf state in July 2012.

The men said they were given electric shocks and had guns held to their heads during a seven-month period in which they were held without trial. Their lawyers also claimed they were forced at gunpoint to sign documents written in Arabic, which none of them understood. The men's allegations of torture –denied by the Emirati police – were raised by David Cameron.

Among the recently released documents is a report from a British torture expert that chronicles the failings of the internal medical "investigation" carried out by the Dubai authorities into the health impacts of Ali's alleged mistreatment.

Analysis of the UAE's investigation by a clinical psychologist, Dr Brock Chisholm, concludes that the report, which was designed to establish whether Ali had been tortured, "does not meet the minimum expected standards" according to the Istanbul Protocol, the international guidelines for the documentation of torture or ill treatment.

Algar added: "Despite an outcry last year over the torture of three British citizens, which saw David Cameron raising their case with the country's ruler, the same brutal practices have continued – Ali and Zeidan are just the latest in a long line of victims. The British government must make crystal clear that the situation is unacceptable, and ensure that both men are released without delay."

Zeidan was studying at the Emirates Aviation College in Dubai when he was arrested on drugs charges four months ago in Sharjah, just over the border in UAE. The charges carry a potential death penalty and are broadly the equivalent of possession with intent to supply, despite the prosecution itself alleging that the Briton was in possession of less than one gram of cocaine.

Zeidan alleges that he was beaten after his arrest and subsequently held incommunicado. He also says he was denied access to his family as well as legal or consular assistance for eight days. During his detention, his lawyers claim, Zeidan was forced to strip naked and was threatened with rape by officers.

Ali, who was arrested in Dubai in May 2013, again for allegedly possessing cocaine, believes he was being framed.

Figures released by the Foreign Office showed that many Britons have fallen foul of the UAE's tough drugs laws. The British embassy in Dubai helped 257 Britons who were arrested or detained on drugs charges in the last year. This represented almost half the embassy's case load.

A study by Reprieve last year, based on interviews with prisoners in Dubai Central Jail, found that more than three-quarters claimed they had suffered physical abuse after their arrest. In addition, 85% said they had been forced to sign documents in a language they did not understand.

Police in the UAE have repeatedly denied claims of torture and of extracting false confessions by force.